function updateItem( id, op, increments, fields ) {

	var allowNegNumbers = false;
	var val = $(id).attr("value");

	if(op != null) {
		if(!(val = parseInt( val )) ) val = 0;
		if(op == "+") {
			val = val + increments;
		} else if( op == "-" ) {
			val = val - increments;
			if(!allowNegNumbers && val < 0) val = 0;
		}
	}

	fields.numberOfItems = val;

	doAjax( "shoppingcart","updateItem", fields );
}

function doAjax( ajax, action, paramsObj ) {

	var params = $.param(paramsObj);

	$.get(
		BASEURL + "/ajax/?ajax=" + ajax + "&action=" + action + (params.length ? "&" + params : ""),
		null,
		function(data) {
			eval(data.script);
		},
		"json"
	);


}